The MMO map allows you to earn XP points much like you do score on the other maps. Once enough XP is earned, you can gain levels just like other RPGs. Unlike scores, the Levels and XP persist through separate play sessions on the map.
There are two quick ways to instantly jump to level 101.
1) Do tricks using the Anti-Gravity Mutator
On the MMO map, activate the Anti-Gravity ability. Once it is active, jump into the air and start spinning forward and to the side simultaneously. After a few seconds you should turn off Anti-Gravity and start descending. Turn on slow motion and stabilize yourself by pressing forward which will automatically put your feet under you again. When you are close to the ground, stick the landing by pressing the jump button.
This should give you a lot of points and levels. If you aren't 101 yet, do it again and maybe spin longer. If you did not receive any levels and gained a negative XP value, then you spun for too long and caused an overflow issue. Just attempt it again and spin for less time.
2) Complete the quest Things Aren't Gonna Lick Themselves
There is no good reason to do the quest, but if you insist on doing it, you'll gain this achievement when it completes.